@RIP Dime:

Exactly! It's the second step added and octave higher from the root note.We don't add it on all strings. 9's are mostly used for powerchording and the only place we add it is just like in the diagram. We play the root note - the 5th and than the 9th step.

If it confuses you with sus2 - in sus2 we REPLACE 3rd with 2nd whereever the 3rd appears in the chord. In 9's we simply add the 9th step (not 2nd - but 9th because it is an octave higher).

I hope this makes things clear.

A little add:

D|--9--|
A|--7--|
E|--5--|

This here is an A9 - A on the 5th fret E string,
E on the 7th fret A string and B on the 9th fret D string. We don't add the 2nd step on the E string but only the 9th step on D string which means it is the 2nd step BUT an octave higher. That's the difference between added 2nd and added 9th.

Yeah - you got it right! Cool! If you listened to Dream Theater stuff they use a lot on 9's in their riffs and they sound awesome to me.

I am glad you understood it the right way! Keep rocking!

Hey man thanks a lot! I am glad these lessons are of some use for anyone!